<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <div class="input-num">
            <button @click="sub">-</button>
            <span>{{num}}</span>
            <button @click="add">+</button>
               <!--1、 开发环境版本，包含了有帮助的命令行警告 -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
        <script>
            var app=new Vue ({
                el:"#app",
                data:{
                    num:1
                },
                methods:{
                    add:function(){
                        if(this.num<10){
                            this.num++;
                        }else{
                            alert('别点啦，最大啦！');
                        }
                    },
                    sub:function(){
                        if(this.num>0){
                            this.num--;
                        }else{
                            alert("别点了，最小了");
                        }
                    }
                }
            })
        </script>
        </div>
    </div>
</body>
</html>